Diy mc stepup

[Frankyc2003]

Good Morning Everyone,

I am about to embark on yet again another DIY project...
This time it won't involve any AC current though!

I have acquired a pair of Stevens & Billington TX1003-20.
And guess what? I want to put them together in a nice box to make my own MC Stepup...

First question to you, very knowledgeable people is, which RCA plugs would you recommend?

Secondly, I am using a LYRA CLAVIS (original from 1992...), and it should see a load of anything below 47KOhm according to manufacturer... So what load would you recommend the cartridge to see on the input?

And finally, do I need to worry about shielding the casing? I am not sure yet, which box I will choose (open to suggestions!)

Thanks a lot in advance for all your input and insights...

Cheers
:cool:

F

[The Grand Wazoo]

I have the Bent Audio Mu step-ups which contain S&B's, but to my ears sound far better than their own effort. The cans are housed in 1/4" thick cylindrical cases made of mu metal.

[Frankyc2003]

I have the Bent Audio Mu step-ups which contain S&B's, but to my ears sound far better than their own effort. The cans are housed in 1/4" thick cylindrical cases made of mu metal.

These are looking lush!
http://theartofsound.net/forum/showthread.php?t=2907

Those loading posts are a great idea!
I wonder how they are wired below the surface?
:scratch:

[NRG]

The TX1003-20 has a 20:1 step up ratio, whats the output impedance of the cartridge? 2 Ohm?

If so it needs to see a load of about 20 ohms give or take a bit. You need to check the current load set on your phono stage, most likely to be 47K.

With a 20:1 step up ratio you need to load the secondary with about 8K to get the cartridge to see 20 Ohm (8000 / 400) So put a 10K resistor in parallel with the Phono 47K load....will get you to 8200 / 400 = 20.5 Ohm....close enough!

[NRG]

...another thing you'll need to check what the overload margin is on your phono stage so you don't exceed it with the 1:20 step-up.

Edit: Should be OK 26db voltage gain gives 5mV input from 0.25mV cartridge output.

[Frankyc2003]

The TX1003-20 has a 20:1 step up ratio, whats the output impedance of the cartridge? 2 Ohm?

If so it needs to see a load of about 20 ohms give or take a bit. You need to check the current load set on your phono stage, most likely to be 47K.

With a 20:1 step up ratio you need to load the secondary with about 8K to get the cartridge to see 20 Ohm (8000 / 400) So put a 10K resistor in parallel with the Phono 47K load....will get you to 8200 / 400 = 20.5 Ohm....close enough!

Thanks for that, so far so good, it does make sense...
Now, for a very stupid question, the 47K resistor, where is it located? Inside my Phono Pre, or do I need to mount it inside the SUT?

And then, a complete curve ball... How about primary loading?
I read on the WAD forum that primary loading doesn't compromise bandwidth as much as secondary loading... Any suggestions, opinions?

[NRG]

Yep, the 47K is in your existing phono but check the specs, you've not mentioned what phono pre you have and I'm assuming it only has a MM input....

Yep, been there with Primary loading, gives an interesting effect. I likened it to a loudness button the treble and bass taking on a very up front , in yer face sort of presentation. Initially its seems to be better, its impressive... but after longer time with it I realized it just wasn't right, fine detail went missing and the midrange was laid too far back...don't know anyone on that original thread still using it.

[Frankyc2003]

I use the MM side of my MingDa MC2006. So I assume the 47K is in there somewhere!

http://i835.photobucket.com/albums/zz275/frankyc2003/insideMC2006_zpsdb1fa6e7.jpg

I couldn't really locate it myself... But if anyone likes to give it a go!

I think I will stick with secondary loading as you suggest, and I will try to implement the same loading binding posts as the Bent Audio Mu SUT. I think it's a neat way of keeping things easy to access and solder free...

;)

[NRG]

Neat, p2p wiring and earth busbar. Unfortunately, I can't follow the input signal wiring from the selector switch. Probably best to stick with your binding post idea for the loading.

[Frankyc2003]

Cheers Neal,

I have actually checked on the Schematic, and we have indeed a 47K resistor across the MM input... So it is in there somewhere!
:lol:

[Frankyc2003]

Good morning everyone,

The TX1003-20 have landed.
http://i835.photobucket.com/albums/zz275/frankyc2003/20130314_072239_zpscdebf70b.jpg

So obviously now the wiring is my main issue since I am missing a correct diagram... I believe they are centre tapped (according to S&B website).

Does anyone here has any idea of what each colour means?

The guy I bought them from suggested that red and green were the input, but that's as far as I got unfortunately...

All help mightily appreciated!

PS. I have also dropped an email to S&B, just in case they might have the diagram handy!

[Frankyc2003]

S&B have been dead silent! Has anyone ever wired these before? Any help is really appreciated!
Ta;)

[Barry]

Francoise,

Do you have acces to a multimeter? If you do then you could measure the resistance between pairs of wires. Since the red and green wires are twisted together and so too are the blue and yellow wires, that would suggest they are the connections to the two transformer windings.

The pair with the lowest resistance will be the primary winding. The pair with the higher resistance will be the secondary winding. Don't expect the resistance of the secondary to be 10x that of the primary, it won't be unless the same gauge wire has been used, which is very unlikely.

I suspect the red/green pair are the primary winding and the blue/yellow pair are the secondary winding. This colour convention is followed by several manufacturers (Partridge for example) with the blue wire being in phase with the red.

As to the other wires, well since the black wre is twisted up with the blue and yellow pair that is most likely the centre tap winding on the secondary. The grey wire is likely to be the inter-winding shield and should be earthed alnog with the metal casing of the transformer.

Trust this is of some help

[Frankyc2003]

Thanks a lot Barry,

The seller just left me a note saying that grey wire is for low gain, and yellow wire for high gain... The plot thickens... Does that mean that grey is the centre tap?

I want to make a 1:20 SUT, which one should I connect? Does it make any sense to you?

:scratch:

[The Grand Wazoo]

Now then, I may be able to help here, but maybe not!
After having an extensive rummage in the piles of old stuff I should have thrown out years ago, I've found some paper copies of some downloads relating to the Mu's that I got from the Bent Audio website. They are a few years old now but they may shed some light.
One of them is the instructions on how to build the Mu SUT kit that John Chapman used to offer.

The trouble is that I can't see any reference to colour coding of wires because his kit came with wiring that he carefully attached numbered labels to and he seems only to refer to numbers in the text.

There were three taps on the transformers - for 14, 20 or 26 dB of gain, that is 1:5, 1:10 and 1:20 ratios respectively.

I think your transformers may have two taps - hence the yellow/high and grey/low comment from the previous owner.

[Barry]

The only way to find out for sure would be to meaure the resistance between the wires.

[Frankyc2003]

Red to green gives me a 0.52 ohm reading. The other pairing are out of range...?

[The Grand Wazoo]

My scanner is not connected at the moment, but I need to try & sort it tomorrow, so if I do, I can scan the bits & bobs of literature I have & send them to you if you'd like them? There is some S&B literature in there too.

[Frankyc2003]

That would be great! Thanks Chris.
:D

[The Grand Wazoo]

OK, if you send me your email address, I'll see what I can do for you.

[Frankyc2003]

Pm sent Chris!
Ta

[Barry]

Red to green gives me a 0.52 ohm reading. The other pairing are out of range...?

From your measurements, the red/green pair look to be the primary winding connections. Since the TX 1003-20 offers a voltage transformation ratio of 20x, I would expect the blue/yellow secondary winding to have a resistance somewhere in the range 10 - 20 Ohm. I'm surprised you found the resistance to be "out of range". :scratch: Can you check this?

What is the resistance between the red and grey wires and between the green and grey wires?

Regards

[Frankyc2003]

What is the resistance between the red and grey wires and between the green and grey wires?

OK I have redone all readings...

between red and green I get 5.3
between red and grey I get 2.7
between green and grey I get 3.5
between grey and green together and red 2.7
thats' in the 200 range of my multimeter.

between blue and yellow 1.07
between grey and black out of range
between black and blue out of range
between black and yellow together and blue 1.07
thats with my multimeter on 20k range...

any clues? or am i getting bonkers:mental:

[Barry]

Hello Francois,

Assuming your measured resistance between the blue and yellow wires is 1.07kOhm (since you have the meter set on the 20k (Ohm) range), your measurements are starting to make sense.

The red and green wires are the primary winding, with the grey wire being the centre tap. (Strictly speaking the red - grey resistance when added to the grey - green resistance should equal the red - green resistance. Your measurements do not agree. Can you check the grey - green resistance? - it should be nearer to 2.7 Ohm.)

The blue and yellow wires are the secondary winding (which if your measurements are correct, uses very fine gauge wire).

The black wire is probably an inter-winding screen. It should be connected to the metalwork of the transformer case and thence to the earth terminal of your preamp.

[Frankyc2003]

Can you check the grey - green resistance? - it should be nearer to 2.7 Ohm.)

The lowest reading I get between green and grey is 3.3 at 200 range...
On both Tx...

:scratch:

But the rest makes sense and thanks for your patience...
:cool:

[Frankyc2003]

So here we go, my attempt at wiring the TX together with a cheap and nasty RCA unit from Maplins...

http://i835.photobucket.com/albums/zz275/frankyc2003/34875d69-c26a-4d2b-a892-aec9118bce09_zpsf785332b.jpg

I followed Barry's recommendations and here we are.
The deck is plugged in, the MingDa is plugged in...

Off we go!

From the onset, the unit is bloody quiet!
A lot quieter than the Rothwell MCL (with Lundhal TX inside), by this I mean the noise floor has suddenly dropped under my feet...
A very nice too.
Only had a few minutes to play with, but so far so good!

Thanks again for all your imput!

[Frankyc2003]

The TX1003-20 has a 20:1 step up ratio, whats the output impedance of the cartridge? 2 Ohm?

If so it needs to see a load of about 20 ohms give or take a bit. You need to check the current load set on your phono stage, most likely to be 47K.

With a 20:1 step up ratio you need to load the secondary with about 8K to get the cartridge to see 20 Ohm (8000 / 400) So put a 10K resistor in parallel with the Phono 47K load....will get you to 8200 / 400 = 20.5 Ohm....close enough!

You were bang on... After a few attempts at playing with resistors...
10K is bang on in terms of performance, fluidity and clarity...

And I also added a 100R between IN ground and Earth Post... It did make a significant difference to the noise floor. The MingDa which so far had a slight hum probs, is now as quiet as my Digital setup...

It's snowing outside, plenty of music to listen to...
I am a happy bunny!

PS. next stage is to get proper connectors and a nice case!

[NRG]

http://theartofsound.net/forum/images/icons/icon14.gif Great! A 10x ratio is a good rule of thumb to go by for loading...

[Reffc]

Just a question for some of you guys. Why do you put your cart loading on the secondaries?

That can cause other problems. In many ways, it's better to load the primary side and just use a cap in parallel on the seocndaries if you want to put some HF damping on the circuit (It's what I'm doing with my own range of SUTs shortly to be launched).

[NRG]

Define 'better'....as noted above its been tried and I found the presentation uneven and plain wrong....it's a bit like adding a loudness control for your cartridge.

[Reffc]

Define 'better'....as noted above its been tried and I found the presentation uneven and plain wrong....it's a bit like adding a loudness control for your cartridge.

It's very simple really. Its preferable to load the cartridge on the primary side without impacting negatively on the performance of the transformer, but it is NOT possible to select an empirical load (either a resistor or a resistor and a capacitor network) on the secondaries without affecting the transformer's performance. Unless you have access to measuring equipment to see what the effects of loading the secondary are on the waveform (signal amplitide and bandwidth) then it's not recommended. This is well documented by companies such as Graham Slee and Rothwell for those very reasons.

There's a lot of debate on DIY forums about this, but the facts remain that the performance of the transformer can be altered by loading the secondaries unless that has been measured and different values tried so that it can be properly implemented. My advice would be that if that kit isn't available, you are safer to load the primary side. The cartridge sees exactly the same load either way and the required damping is achieved. If it sounds better to your ears to load the secondary, then the only differences which can explain this is the altering of the transformer's measured performance. That doesn't mean to say it's been improved, only that the output is varied from what the designer intended and colouration of some sort of signal loss has induced the change in sound. If that change sounds better to you, then perhaps that's all that really matters for you.

The other explanation of course is that without measuring the effects, you have hit on the perfect secondary load combination but this is usually achieved only with very specific resistive and capacitative loads on the secondaries and these are usually arrived at by measurement since it is impossible to guess. The other point worth mentioning is that no two SUT designs are the same. They all vary in inductance, leakage, capacitance, bandwidth and response. Many will "ring" but usually well above audible frequencies. Point is, what works for one 1:10 or 1:20 SUT is no guarantee that the same results can be had with another.

Just my tuppenceworth having gone through the mill of developing an SUT and having seen the results of various loading methods.

[Firebottle]

:goodthread:

[Ammonite Audio]

What a helpful thread this has been! Thanks to Neal's explanations, I can finally do the maths regarding SUT impedance etc and, notwithstanding the fact that there is more to a good SUT than just matching impedances, I now see that my Ortofon ST-80SE is very precisely optimised for an Ortofon cartridge, but is far from ideal for my Benz Wood SL which likes to see around 300 ohms and it is simply not giving its best via the ST-80SE. I understand that altering (increasing) the input impedance of my phono amp should make the Benz happy, but I have pretty much decided to try a different SUT altogether, most likely one from Audio Note (their 64ohm, 22dB gain SUTs will (simplistically) load the Benz at near enough 300 ohms).

[NRG]

I will stick with secondary loading, I've tried many SUT and always found the same effect, primary side loading sounds wrong, unbalanced in response. Many SUT manufactures do in fact recommend secondary loading. I've also measured the square wave performance for many of them and always found the best response was with secondary loading. Ive added correction circuits before to tame excessive ringing but nearly always found the sound quality suffered, what seemingly is the correct technical thing to do on paper does not always work out in reality. Just IME.

[Reffc]

I will stick with secondary loading, I've tried many SUT and always found the same effect, primary side loading sounds wrong, unbalanced in response. Many SUT manufactures do in fact recommend secondary loading. I've also measured the square wave performance for many of them and always found the best response was with secondary loading. Ive added correction circuits before to tame excessive ringing but nearly always found the sound quality suffered, what seemingly is the correct technical thing to do on paper does not always work out in reality. Just IME.

That's fair comment and I'd support your position as it's what's worked for you. What this demonstrates clearly IMHO is that the quality of the transformer is key. You shouldn't get any nasties loading the primary side if the tranny you're working with measures well in the first place. What I totally accept is that due to the sensitivity of transformers to secondary loading, you can get a smooth overall response but usually at the expense of reduced signal amplitude. If that's not a concern, then it's easy to see why 2ndary loading has been popularised. Doesn't make it right mind!

[Barry]

Glad to hear it's working well Francois,

However I'm a little puzzled. From your photograph it seems you are not using the grey wires that are the primary winding centre tap. This means the transformers are operating with a 10:1 ratio.

10kOhm in parallel with the amplifier's input load of 47kOhm will give an effective load of 8245.6 Ohm. This is effectively in series with the secondary winding resistance of 1070 Ohm (your measurement), making 9315.6 Ohm.

With a 10:1 ratio, the secondary impedance is transformed down to 9315.6/100 = 93.16 Ohm, and this appears in series with the primary winding resistance of 6 Ohm (2.7 + 3.3 Ohm, again your measurements), making an effective load to your cartridge of 99.16 Ohm.

In my experience most moving coil cartridges like to be loaded with at least 100 Ohm. Too little, and the sound appears 'flattened' (or 'sat on'), with constrained treble; too much above 100 Ohm and the treble is a bit too 'lively'. I tend to experiment with values between 100 and 400 Ohm.

So I can well understand why you feel a secondary loading resistor of 10kOhm is just right.



I'm not clear as to whether it is better to load the primary or secondary windings. Transformer manufacturers usually quote a primary load which is quite specific, whereas the recommended secondary load will be much wider. For example, the Haufe transformers T-7883 and T-890 have a recommended primary load of 40 Ohms (and so are ideal for the Denon 103 cartridge), yet have a recommended secondary loading of > 30kOhm. From what I have read about Stevens & Billington transformers, they do not need a Zobel network to suppress ringing. It's all down to the design of the transformer.

As in all things - if it sounds right to you, then stick with your present arrangement.

[Frankyc2003]

Just to be sure, I will try tonight to load the cartridge on the primary side of the TXs.

I will keep you posted...

Cheers
:cool:

[Reffc]

Glad to hear it's working well Francois,

However I'm a little puzzled. From your photograph it seems you are not using the grey wires that are the primary winding centre tap. This means the transformers are operating with a 10:1 ratio.

10kOhm in parallel with the amplifier's input load of 47kOhm will give an effective load of 8245.6 Ohm. This is effectively in series with the secondary winding resistance of 1070 Ohm (your measurement), making 9315.6 Ohm.

With a 10:1 ratio, the secondary impedance is transformed down to 9315.6/100 = 93.16 Ohm, and this appears in series with the primary winding resistance of 6 Ohm (2.7 + 3.3 Ohm, again your measurements), making an effective load to your cartridge of 99.16 Ohm.

In my experience most moving coil cartridges like to be loaded with at least 100 Ohm. Too little, and the sound appears 'flattened' (or 'sat on'), with constrained treble; too much above 100 Ohm and the treble is a bit too 'lively'. I tend to experiment with values between 100 and 400 Ohm.

So I can well understand why you feel a secondary loading resistor of 10kOhm is just right.



I'm not clear as to whether it is better to load the primary or secondary windings. Transformer manufacturers usually quote a primary load which is quite specific, whereas the recommended secondary load will be much wider. For example, the Haufe transformers T-7883 and T-890 have a recommended primary load of 40 Ohms (and so are ideal for the Denon 103 cartridge), yet have a recommended secondary loading of > 30kOhm. From what I have read about Stevens & Billington transformers, they do not need a Zobel network to suppress ringing. It's all down to the design of the transformer.

As in all things - if it sounds right to you, then stick with your present arrangement.

Good post.

You've hit on something that had me puzzled for ages until I looked into it in more depth. Most SUT manufacturers seem to load the primaries with some also adding a Zobel network to the secondaries (typically 10 to 20KOhms for the resistor) in an attempt to cure ringing. For good transformer design, this shouldn't really be needed since the instability from what I've seen only starts to occur a fair way up the bandwidth, more often than not out of audible hearing range. The transformers I've had developed are an inter-leaved design full bandwidth and don't exhibit any ringing within the audible bandwidth, so I know that I can simply load the primaries and not fret.

You're also right in that most MC cartridges like to see 100 Ohms or more but its not an exact science. You could load to say 500Ohms and the main difference wouldn't be in the FR but in mechanical damping (ie damping decreases when you start to go significantly over the recommended load) but for most carts, anywhere between 100 and 400 Ohms should be just fine. EAR supply their 834 loaded by the RIAA stage only so assuming it's a 1:10 ratio SUT, the primary sees 470 Ohms (someone may know the actual step up ratio but I think it's between 1:10 and 1:15).

One issue which I don't think has been mentioned so far is that going too low on the loading doesn't just affect treble response but signal amplitude. The lower the loading the greater the current demand on the cartridge coils, the greater the current flowing through the coils, the greater the flux (electro-magnetic) damping. In theory, a load of zero Ohms would result in zero signal! Load can never be zero, but you get the point. Under-loading the cart defeats the purpose of the step up as you lose voltage gain. That's one of the reasons that a recommended minimum load is specified and its a reason why you don't need to worry if it's not exact. Getting to the recommended load impedance plus 50 or even a few hundred Ohms shouldn't have too much bearing on response, but the acid test is to try it and see, just don't go under the recommended load.

[Frankyc2003]

Well I have to say that this little DIY project I started has cast a very bright light on a very obscure area of the Vinyl art... Something that was as obscure and cryptic as cartridge loading has now become a lot clearer!
So thanks to everyone participating!
I have to also point out a really nice page done by Jim Hagerman with some calculators for those (like me) mathematically challenged...

:cool:

[Frankyc2003]

OK, having played around with primary loading,
I have to say,
IMHO
It didn't work for me.

Something didn't sound right when I connected the resistor in parallel with the cartridge on the primary side of the TXs. I was showing 20R to the cartridge...
It added like a kind of ringing noise to everything...

Tried a few different recordings and all displayed to a certain level the same traits.

SO back to an old 10K resistor on the secondary side of things, and everything sings again to my ears...

Different strokes, different folks...

[Reffc]

OK, having played around with primary loading,
I have to say,
IMHO
It didn't work for me.

Something didn't sound right when I connected the resistor in parallel with the cartridge on the primary side of the TXs. I was showing 20R to the cartridge...
It added like a kind of ringing noise to everything...

Tried a few different recordings and all displayed to a certain level the same traits.

SO back to an old 10K resistor on the secondary side of things, and everything sings again to my ears...

Different strokes, different folks...


20R is way too low for most cartridges so not surprised you didn't like it! What cartridge are you using?

[Frankyc2003]

Its a Lyra Clavis. Original from 1992...
It has a 2 ohm internal.
:scratch:

[NRG]

Francois, unless you have access to a signal generator and oscilloscope stick with secondary loading. To get anywhere with primary loading I would recommend replacing the 47K internal load resistor in your pre-amp with 1Meg ohm. Then you need to arrange to feed the SUT via a resistor network a 1KHz square wave and measure the response on the SUT secondary. Then construct a snubber/zobel network across the SUT secondary to dampen out the transformer ringing that will be present.

The primary load resistor will be in series with the primary DC resistance of the SUT, so your 20R wont actually be what the cartridge sees....although it wont be that far out...21 ohm in your case! :D Also it will be in parallel with the reflected load from your preamp so that needs to be calculated as well, just placing a load resistor on the primary may not work in the vast majority of cases.

Also, your cartridge has such a low output impedance it will exasperate transformer ringing, a higher o/p impedance will help lessen the issue....lastly, if you change your cartridge you would need to rework the Zobel circuit and also if you changed the SUT!

Now you can see why in practice, despite being technically 'incorrect' secondary loading works and is easier to implement.

[Frankyc2003]

Again, some very thorough explanations Neal!
I shall keep that in mind, but for now, as you suggested I will stick to secondary loading... fully knowing it might not be right...

Thanks to Reffc (Paul) also for some precious advice! Looking forward to see your range of SUT!

:cool:

[NRG]

Just for completeness, I've just gone back to try loading of the primary with a snubber network...its something I forgot to do last time I tried it....so I may have to eat my words! :doh: But I'm full of cold at the moment so wont make any judgement until I feel better. :D

I optimized the snubber for a low impedance cartridge <5 Ohm

This is with no snubber:

http://i94.photobucket.com/albums/l82/_NRG_/other/PhonoII/5Ohm_No_Zobel.jpg

With snubber:

http://i94.photobucket.com/albums/l82/_NRG_/other/PhonoII/5Ohm_Zobel.jpg

Note, these images are zoomed in to highlight the change, this is what the second shot above looks like normally:

http://i94.photobucket.com/albums/l82/_NRG_/other/PhonoII/14Ohm_Zobel_zoom_out.jpg

Moving to a higher output cartridge like a DL103R the ringing without the snubber is not as bad:

http://i94.photobucket.com/albums/l82/_NRG_/other/PhonoII/14Ohm_No_Zobel.jpg

...and with the snubber output is slightly less and a bit more rounded but still very good.

http://i94.photobucket.com/albums/l82/_NRG_/other/PhonoII/14Ohm_Zobel.jpg

I've not tried a higher impedance cartridge like the standard DL103 but I suspect the snubber would need to be reworked to get a good response.

[Frankyc2003]

Just a very quick update to post a picture of the finished article...

http://i835.photobucket.com/albums/zz275/frankyc2003/20130326_220636_zpsa088ae70.jpg

Not the prettiest casing, but it work for me...

What a fantastic journey this has been, and now I am contemplating hours and hours of beautiful vinyl replay!
:cool:

[Reffc]

Just for completeness, I've just gone back to try loading of the primary with a snubber network...its something I forgot to do last time I tried it....so I may have to eat my words! :doh: But I'm full of cold at the moment so wont make any judgement until I feel better. :D

I optimized the snubber for a low impedance cartridge <5 Ohm

This is with no snubber:

http://i94.photobucket.com/albums/l82/_NRG_/other/PhonoII/5Ohm_No_Zobel.jpg

With snubber:

http://i94.photobucket.com/albums/l82/_NRG_/other/PhonoII/5Ohm_Zobel.jpg

Note, these images are zoomed in to highlight the change, this is what the second shot above looks like normally:

http://i94.photobucket.com/albums/l82/_NRG_/other/PhonoII/14Ohm_Zobel_zoom_out.jpg

Moving to a higher output cartridge like a DL103R the ringing without the snubber is not as bad:

http://i94.photobucket.com/albums/l82/_NRG_/other/PhonoII/14Ohm_No_Zobel.jpg

...and with the snubber output is slightly less and a bit more rounded but still very good.

http://i94.photobucket.com/albums/l82/_NRG_/other/PhonoII/14Ohm_Zobel.jpg

I've not tried a higher impedance cartridge like the standard DL103 but I suspect the snubber would need to be reworked to get a good response.

Interesting results with the test SUT; this may not be the same for all SUTs though as some are more prone to ringing and do have some electrical damping for that reason. It would be interesting for your test SUT to repeat the tests with the secondary loaded as the meaningful comparison is in the primary v's secondary loading scenario. As previously mentioned, when the SUT that I'm having developed was loaded on the primary, there was no ringing within the audible frequency band.

[NRG]

Theres no ringing in the audio band here either, that ringing is way out past 100Khz but its affects can be heard in the audio band. All transformers suffer from some interwinding capacitance and leakage inductance so ringing is inevitable at some frequency. Loading the secondary still had some ringing but with a low output impedance cartridge it's possible to load the secondary more but still maintain a 10x or so loading and snub the ringing but as you noted you lose gain, quite a lot in fact.

With higher output impedance the loading resistor has to increase in value and then up goes the ringing. I've tweaked the setup more since the above scope shots and now have two switchable ccts I can use depending on the cartridge o/p impedance, the loading is now switchable on the primary.

So humble pie time, it works and works well the presentation is far more focussed, balanced and tuneful...a real step-up (couldn't resist!) in performance. Unfortunately, not everyone is going to be able to tune the cct without a test rig and any values for one SUT will not apply to a different one...

[Reffc]

Theres no ringing in the audio band here either, that ringing is way out past 100Khz but its affects can be heard in the audio band. All transformers suffer from some interwinding capacitance and leakage inductance so ringing is inevitable at some frequency. Loading the secondary still had some ringing but with a low output impedance cartridge it's possible to load the secondary more but still maintain a 10x or so loading and snub the ringing but as you noted you lose gain, quite a lot in fact.

With higher output impedance the loading resistor has to increase in value and then up goes the ringing. I've tweaked the setup more since the above scope shots and now have two switchable ccts I can use depending on the cartridge o/p impedance, the loading is now switchable on the primary.

So humble pie time, it works and works well the presentation is far more focussed, balanced and tuneful...a real step-up (couldn't resist!) in performance. Unfortunately, not everyone is going to be able to tune the cct without a test rig and any values for one SUT will not apply to a different one...

A very thoughtful response and your conclusion is very pertinent in that what's good for one SUT may not necessarily be good for another. It's impossible to generalise about the loading I think save to say that in theory, you should get the SUT performing closer to design spec loading the primary BUT this may not suit all SUTs for some of the reasons you've alluded to. Most well designed SUTs should place the ringing high up out of the audible bandwidth but where that's difficult to achieve, a cap of the correct value can help smooth the response within acceptable limits.